The present invention relates generally to securing and deploying an articulated set of elements on a spacecraft.
Articulated sets of elements such as solar generator panels, antennas, heat radiators, spacer arms, etc. are secured on spacecraft. This is known in the art.
In the present context, the expression xe2x80x9csolar generator panelsxe2x80x9d refers to all the plane structures of the solar generator having optical, thermal or photovoltaic active surfaces, and in particular:
panels supporting an array of identical or different photovoltaic cells for converting solar energy into electrical energy;
reflector panels which concentrate solar radiation onto the previous panels by means of a coating with appropriate properties; and
panels used for their surface thermo-optical characteristics (heat radiators).
During transfer from the ground to a basic transfer orbit that the spacecraft occupies before it is moved to the geosynchronous orbit, or even during transfer from the ground to the geosynchronous orbit, the elements are folded and pressed against the body of the spacecraft in a configuration referred to as the xe2x80x9cstacking configurationxe2x80x9d.
Putting the elements into operational service, for example when the vehicle is a satellite that has been moved to its service orbit, entails moving each element to a deployed position relative to the body of the vehicle: this is referred to as xe2x80x9cunstackingxe2x80x9d.
Securing systems including at least one retaining member passing through each element are usually employed for this purpose.
One such system is described in the patent DE-A-3 106 099 in particular. To prevent a retaining member damaging said elements by coming into contact with them during their deployment, the above prior art document proposes to move the retaining member outwards once it has been cut, to disengage it from said folded elements. To this end, drive spring means are disposed-between the retaining member and the outermost element of the articulated set. In the folded position of the set of elements, the drive spring means are charged and the retaining member prevents them from relaxing. However, when the retaining member has been broken, the spring means relax to move the retaining member into a position in which it is disengaged from said elements.
In similar systems, to absorb the shock due to the ejection of the retaining member after it is cut, the retaining member is thrown onto a honeycomb structure shock absorber. A honeycomb structure shock absorber cannot retain the retaining member in a given position, for example on the rear face of a solar panel, in order to prevent it casting shadows on the photovoltaic cells of the panel, and more generally to prevent it interfering with the operation of the element that has been deployed.
Also, to carry out tests on the ground under different conditions it is necessary to have several shock absorbers suitable for the range of energies to be absorbed. What is more, the shock absorbers are consumable (non-reusable).
The present invention aims in particular to overcome the above disadvantages.
To this end, it proposes a securing system for securing an element to a structure in a folded position, which element can assume either said folded position or a deployed position relative to the structure, said system comprising:
a retaining member passing through the element in the folded position and connected at one end to said structure and bearing at the other end on an external side of the element;
means for rupturing said retaining member or its connection to said structure when the element is required to move from its folded position to its deployed position; and
a mechanism including drive means for pulling the corresponding part of the retaining member outwards through the element after actuation of said rupture means, the retaining member having an enlargement in the part which is pulled by the drive means, the system further comprising a holding and shock-absorbing device mounted on the element and including a barrel with an orifice passing through it adapted to receive the retaining member concentrically, a plurality of cut-outs in the wall of the barrel forming a plurality of spring tongues adapted to be bent wholly or partially towards the inside of the barrel in order to come into contact with the part of the retaining member which is pulled by the drive means, the enlargement being adapted to cooperate with said tongues to hold the retaining member after actuation of the drive means.
Because of the above features, the shock due to the ejection of the retaining member is absorbed and the retaining member is held in a required position by a single one-piece device.
Moreover, because it is possible to bend the spring blades wholly or partly towards the inside of the barrel, numerous adjustments are catered for, enabling shock to be absorbed as required.
Also, the device can absorb a very wide range of energies.
In a preferred embodiment, the blades can be returned to their original position within the envelope defined by the barrel.
To this end the holding and shock-absorbing device can be machined from a highly elastic material. This produces a non-consumable device that can therefore be reused.
According to preferred features, which may be combinable:
the cut-outs have an inverted U-shape;
the spring tongues are mutually offset in the longitudinal direction of the barrel;
the spring tongues are arranged in a staggered configuration;
the barrel has at one end an annular projection penetrating into the orifice perpendicularly to the longitudinal axis of the barrel and having an inside end which has a rounded profile in elevation;
the barrel is made from an alloy of copper and beryllium;
the shape of the enlargement can be varied to enable the retaining member to be used under different conditions of use;
the element is an outermost panel of a set of panels of a solar generator hinged to each other and to the structure, the panels being superposed in the folded position of the set and at least substantially aligned with each other end-to-end in the deployed position of the set, and at least one retaining member passing through the panels in the folded position and having an enlargement adapted to cooperate with spring tongues of a corresponding holding and shock-absorbing device;
the barrel has an external flange for immobilizing the barrel which is located between the outermost panel and the directly adjacent panel in the folded position of the set of panels;
the mechanism includes additional drive means acting in the opposite direction to the drive means and adapted to move each retaining member which has been released into a position, and holding it in that position, relative to said outmost panel which, at least when said set of panels is in a deployed position, is at least substantially the same as the position which the retaining member occupied in the folded position of the set of panels before actuation of the rupture means, and the barrel having an outside flange on which the drive means and the additional drive means bear; and
the drive means and the additional drive means are coil springs through which the retaining member passes.
The present invention also relates to the holding or position maintaining device as such.